Add --partition M/N to distribute builds

README.md

@@ -216,6 +216,9 @@ OPTIONS:
         --keep-going
             Keep going on failure.
 
+        --partition <M/N>
+            Partition runs and execute only its subset according to M/N.
+
         --log-group <KIND>
             Log grouping: none, github-actions.
 

src/cli.rs

@@ -13,7 +13,7 @@ use lexopt::{
     ValueExt,
 };
 
-use crate::{term, version::VersionRange, Feature, LogGroup, Rustup};
+use crate::{term, version::VersionRange, Feature, LogGroup, Partition, Rustup};
 
 pub(crate) struct Args {
     pub(crate) leading_args: Vec<String>,
@@ -53,6 +53,8 @@ pub(crate) struct Args {
     pub(crate) clean_per_version: bool,
     /// --keep-going
     pub(crate) keep_going: bool,
+    /// --partition
+    pub(crate) partition: Option<Partition>,
     /// --print-command-list
     pub(crate) print_command_list: bool,
     /// --version-range/--rust-version
@@ -155,6 +157,7 @@ impl Args {
         let mut clean_per_run = false;
         let mut clean_per_version = false;
         let mut keep_going = false;
+        let mut partition = None;
         let mut print_command_list = false;
         let mut no_manifest_path = false;
         let mut locked = false;
@@ -308,6 +311,7 @@ impl Args {
                 Long("clean-per-run") => parse_flag!(clean_per_run),
                 Long("clean-per-version") => parse_flag!(clean_per_version),
                 Long("keep-going") => parse_flag!(keep_going),
+                Long("partition") => parse_opt!(partition, false),
                 Long("print-command-list") => parse_flag!(print_command_list),
                 Long("no-manifest-path") => parse_flag!(no_manifest_path),
                 Long("locked") => parse_flag!(locked),
@@ -571,6 +575,8 @@ impl Args {
             None => LogGroup::auto(),
         };
 
+        let partition = partition.as_deref().map(str::parse).transpose()?;
+
         if no_dev_deps || no_private {
             let flag = if no_dev_deps && no_private {
                 "--no-dev-deps and --no-private modify"
@@ -620,6 +626,7 @@ impl Args {
             clean_per_run,
             clean_per_version,
             keep_going,
+            partition,
             print_command_list,
             no_manifest_path,
             include_features: include_features.into_iter().map(Into::into).collect(),
@@ -813,6 +820,7 @@ const HELP: &[HelpText<'_>] = &[
         "This flag can only be used together with --version-range flag.",
     ]),
     ("", "--keep-going", "", "Keep going on failure", &[]),
+    ("", "--partition", "<M/N>", "Partition runs and execute only its subset according to M/N", &[]),
     ("", "--log-group", "<KIND>", "Log grouping: none, github-actions", &[
         "If this option is not used, the environment will be automatically detected."
     ]),

src/main.rs

@@ -639,6 +639,22 @@ impl FromStr for LogGroup {
     }
 }
 
+pub(crate) struct Partition {
+    index: usize,
+    count: usize,
+}
+
+impl FromStr for Partition {
+    type Err = Error;
+
+    fn from_str(s: &str) -> std::result::Result<Self, Self::Err> {
+        match s.split('/').map(str::parse::<usize>).collect::<Vec<_>>()[..] {
+            [Ok(index), Ok(count)] if 0 < index && index <= count => Ok(Self { index, count }),
+            _ => bail!("bad or out-of-range partition: {s}"),
+        }
+    }
+}
+
 fn exec_cargo(
     cx: &Context,
     id: &PackageId,
@@ -672,7 +688,26 @@ fn exec_cargo_inner(
     if progress.count != 0 && !cx.print_command_list && cx.log_group == LogGroup::None {
         eprintln!();
     }
-    progress.count += 1;
+
+    let new_count = progress.count + 1;
+    let mut skip = false;
+    if let Some(partition) = &cx.partition {
+        if progress.count % partition.count != partition.index - 1 {
+            let mut msg = String::new();
+            if term::verbose() {
+                write!(msg, "skipping {line}").unwrap();
+            } else {
+                write!(msg, "skipping {line} on {}", cx.packages(id).name).unwrap();
+            }
+            write!(msg, " ({}/{})", new_count, progress.total).unwrap();
+            let _guard = cx.log_group.print(&msg);
+            skip = true;
+        }
+    }
+    progress.count = new_count;
+    if skip {
+        return Ok(());
+    }
 
     if cx.clean_per_run {
         cargo_clean(cx, Some(id))?;
@@ -690,7 +725,7 @@ fn exec_cargo_inner(
     } else {
         write!(msg, "running {line} on {}", cx.packages(id).name).unwrap();
     }
-    write!(msg, " ({}/{})", progress.count, progress.total).unwrap();
+    write!(msg, " ({}/{})", new_count, progress.total).unwrap();
     let _guard = cx.log_group.print(&msg);
 
     line.run()

tests/long-help.txt

@@ -186,6 +186,9 @@ OPTIONS:
         --keep-going
             Keep going on failure.
 
+        --partition <M/N>
+            Partition runs and execute only its subset according to M/N.
+
         --log-group <KIND>
             Log grouping: none, github-actions.
 

tests/short-help.txt

@@ -46,6 +46,8 @@ OPTIONS:
                                          command
         --clean-per-version              Remove artifacts per Rust version
         --keep-going                     Keep going on failure
+        --partition <M/N>                Partition runs and execute only its subset according to
+                                         M/N
         --log-group <KIND>               Log grouping: none, github-actions
         --print-command-list             Print commands without run (Unstable)
         --no-manifest-path               Do not pass --manifest-path option to cargo (Unstable)